Some super yachts are bigger than destroyers. The longest is 590 ft long and 13,136 tons. The biggest is 20,000 tons. The top ten are all bigger than 10,000 tons.

Warships and yachts are totally different vessels, there is no place on the latter for sensors or weapons.

There are plenty of sensors on yachts. Hell, my father’s dingy has a sensor on it.